(I) Field of the Invention
The present invention relates to the field of gas analysis systems and pertains more particularly to systems for analyzing the content of at least one element of the atmosphere in an enclosure used for soldering or tinning by means of a metal alloy, these soldering or tinning operations using the assistance of a chemical flux which conventionally comprises one or more components among acids, alcohols, or resins, especially rosins.
(II) Description of the Related Art
Soldering and tinning operations are carried in particular in electronics. Examples include soldering of electronic components on a circuit, soldering of circuits in module backplanes, or else termination tinning of electronic components.
The role of the fluxing is then to clean the metal surfaces to be soldered or tinned (degreasing, deoxidation, decontamination of absorbed layers, etc.), the purpose of this being to facilitate the subsequent wetting of these surfaces by the solder.
This fluxing operation is therefore, most commonly, carried out by means of chemical fluxes, often obtained from a resinous base to which, in particular, acid components are added.
It will therefore be noted that two of the most commonly used methods for carrying out such soldering operations in electronics are called "wave soldering" and "reflow soldering."
In the first case of wave-soldering machines, the design of these machines is such that the parts to be soldered or tinned are brought into contact with one or more liquid solder waves obtained by making the solder bath contained in a tank flow through a nozzle. The parts (circuit, component) have generally been fluxed beforehand in a zone upstream of the machine, by means of a flux spray or foam, the fluxing operation being followed by a preheating operation which is done to activate the fluxes deposited beforehand on the circuit and to preheat the circuits or components before their arrival in the hot soldering zone.
In the case of the second type of method, called reflow soldering, which moreover combines several techniques under this name, it is not a bath of liquid solder that is used but a solder paste containing the solder alloy, in which paste formulation the chemical flux is included, which paste is deposited on the substrate and to which paste a certain amount of heat allowing the metal alloy to melt is supplied; usually, this heat transfer is carried out in a continuous oven.
It is becoming increasingly commonplace for industrial gas users (electronics, heat treatment, food, etc.) to be required to analyze one or more components of the atmosphere that they employ at a given user station, so as to be in a position to carry out a complete quality control of the parts treated, complete quality control assuming, in particular, that it is possible to know under which atmosphere conditions each part has been treated.
Depending on the intended application, safety conditions (risks of explosion) also apply.
Gas consumers therefore usually want to be able to know these atmosphere conditions, or indeed to display them, to archive them, to have traceability and even to process these values thus archived.
It is therefore considered necessary to be able to be in a position to offer industrial gas consumers analytical methods and equipment allowing gas samples to be taken at the various analysis points monitored in the enclosure used for the treatment, making it possible to minimize the response time of the analyzer or analyzers in question and to ensure that the analytical bay is provided with gas samples which are representative of the atmosphere in the enclosure.
By way of illustration, reference may be made to the following documents in the name of the Applicant, which also relate to this field of atmosphere analysis or of atmosphere regulation in soldering or tinning enclosures: FR 98-07498 or EP-A839,599.
The work that Applicant has conducted in this field has raised questions about the reliability of the analytical systems currently present in such soldering or tinning plants, and especially the information in terms of residual oxygen content of the atmosphere in the enclosure for operations carried out under nitrogen.
These uncertainties raise serious doubts regarding the production quality from the soldering or tinning machines in question.